/**
 * this is the low-level implementation of the E1.31 (sACN) protocol
 */

import * as assert from 'assert';

/* eslint-disable lines-between-class-members, no-bitwise, no-control-regex */

const ACN_PID = Buffer.from([
  0x41,
  0x53,
  0x43,
  0x2d,
  0x45,
  0x31,
  0x2e,
  0x31,
  0x37,
  0x00,
  0x00,
  0x00,
]);

enum RootVector {
  DATA = 4,
  EXTENDED = 8,
}
enum FrameVector {
  DATA = 2,
}
enum DmpVector {
  DATA = 2,
}

/* eslint-disable camelcase */

// enum ExtendedFrameVector { SYNC = 1, DISCOVERY = 2 }

export class Packet {
  /* root layer */
  private readonly root_vector: RootVector;
  private readonly root_fl: number;
  private readonly preambleSize: number;
  private readonly postambleSize: number;
  private readonly acnPid: Buffer;
  readonly cid: Buffer; // unique id of the sender

  /* framing layer */
  private readonly frame_vector: FrameVector;
  private readonly frame_fl: number;
  readonly options: number;
  readonly sequence: number;
  readonly sourceName: string;
  readonly priority: number; // 0 to 200; default 100
  readonly syncUniverse: number; // universe used for annoucing timesync
  readonly universe: number;

  /* DMP layer */
  private readonly dmp_vector: DmpVector;
  private readonly dmp_fl: number;
  private readonly type: number;
  private readonly firstAddress: number;
  private readonly addressIncrement: number;
  readonly propertyValueCount: number;
  private readonly startCode: number;
  readonly slotsData: Buffer;

  public constructor(
    private readonly buffer: Buffer,
    public readonly sourceAddress?: string,
  ) {
    /* root layer */
    this.root_vector = this.buffer.readUInt32BE(18);
    this.root_fl = this.buffer.readUInt16BE(16);
    this.acnPid = this.buffer.slice(4, 16);
    this.preambleSize = this.buffer.readUInt16BE(0);
    this.postambleSize = this.buffer.readUInt16BE(2);
    this.cid = this.buffer.slice(22, 38);

    /* frame layer */
    this.frame_vector = this.buffer.readUInt32BE(40);
    this.frame_fl = this.buffer.readUInt16BE(38);
    this.options = this.buffer.readUInt8(112);
    this.sequence = this.buffer.readUInt8(111);
    this.sourceName = this.buffer
      .toString('ascii', 44, 107)
      .replace(/\x00/g, '');
    this.priority = this.buffer.readUInt8(108);
    this.syncUniverse = this.buffer.readUInt16BE(109);
    this.universe = this.buffer.readUInt16BE(113);

    /* DMP layer */
    this.dmp_vector = this.buffer.readUInt8(117);
    this.dmp_fl = this.buffer.readUInt16BE(115);
    this.type = this.buffer.readUInt8(118);
    this.firstAddress = this.buffer.readUInt16BE(119);
    this.addressIncrement = this.buffer.readUInt16BE(121);
    this.propertyValueCount = this.buffer.readUInt16BE(123);
    this.startCode = this.buffer.readUInt8(125);
    this.slotsData = this.buffer.slice(126);

    this.validate();
  }

  private validate(): void | never {
    // ascertains that this packet implements ACN
    assert.deepStrictEqual(this.acnPid, ACN_PID);

    // ascertains that this packet is a DATA packet
    assert.strictEqual(this.root_vector, RootVector.DATA);
    assert.strictEqual(this.frame_vector, FrameVector.DATA);
    assert.strictEqual(this.dmp_vector, DmpVector.DATA);

    // constants within the UDP overhead
    assert.strictEqual(this.type, 0xa1); // = 61
    assert.strictEqual(this.firstAddress, 0);
    assert.strictEqual(this.addressIncrement, 1);
    assert.strictEqual(this.startCode, 0);
    assert.strictEqual(this.preambleSize, 0x0010); // = 16
    assert.strictEqual(this.postambleSize, 0);
  }

  // TODO: For octet 112 (options): Bit 7 = Preview_Data / Bit 6 = Stream_Terminated / Bit 5 = Force_Synchronization
  // public getOption(option: number): boolean {
  //   return !!(this.options & (1 << (option % 8)));
  // }
}